One day, I tried to disassemble my hydraulic braking system (Tektro HDC 300) having a goal of dipping the brake pads in alcohol. Well, I had somehow managed to separate the pads and the spring like metal object. But at one stage, after I squeezed the brake lever for a couple of times, one of the two pistons came out and all the oil got spilled... now my brake doesn't work at all. How can I fix it?

It can be noted that I feel no resistance while pressing brake lever? Is this normal under this circumstance? Will I have to change the whole brake set, or will just refilling with oil be enough?

  • Ahnaf, what happened to your bike before you had this problem?
    – Ben
    Nov 4, 2016 at 14:39
  • I had ridden my friend's bike having shimano hydraulics, and his brakes were supplying much better and harder than these of mine..that's made me think that my brake pads have come in contact with external oil which I had to clean . Nov 5, 2016 at 10:40

1 Answer 1


If you are going to do it yourself - you will need a hydraulic brake bleed kit. You basically need to replenish the fluid in the hydraulic system. This will either be mineral oil or Dot brake fluid. Check with your brake manufacturer which it is.

There is a technique and procedure to bleeding brakes as well. Weigh up the cost of doing it yourself - or just paying an experienced cycle mechanic to do it. Its a fairly standard job and shouldn't take long at all - especially if it is only one brake. Most hydraulic brakes are maintenance free - in that the system is sealed and air does not get into the system.

Unfortunately, you found to your cost - by removing the pads and pressing the levers - you popped the pistons out of their seating (and seals) which leaked all the fluid from the system. A tip would have been to wedge something between the pistons of the padless caliper - in case you accidentally knocked or pulled the brake lever.

  • 1
    It's unlikely to use DOT5: this fluid is rare in hydraulic brakes for bikes. Most likely it'll use mineral oil or a poly-glycol-based DOT fluid (3, 4, or 5.1). Nov 4, 2016 at 13:11
  • Yes. Sorry I'm a Shimano user. I remember it being DoT fluid in the other systems but not the exact numbers. 5.1 rings a bell but worth checking
    – OraNob
    Nov 4, 2016 at 13:29
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    Tektro brakes are mineral oil. Nov 4, 2016 at 15:59
  • Hey, is it right to rub the brake pads with sandpaper to clean them after taking them out of the calipers? Nov 5, 2016 at 10:42
  • Not heard that one. If the pads are contaminated with oil - I've held them over a cooker flame to burn off the oil. You can also bake them on a sheet of grease proof paper in an oven with the pads faced down.
    – OraNob
    Nov 6, 2016 at 0:18

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